Rock drill feeding mechanism



July 13, 1937. G. c. PEARSON ET Al. 2,086,634

ROCK DRILL FEEDING MECHANISM Filed March 12, 1954 4 Sheets-Sheet l ATTORNY.

July 13, 1937. G. c. PEARSON ET AL. f 2,086,634

Rocx DRILL FEEDING MECHANISM Filed March l2, 1954 4 Sheets-Sheet 2 6057A/ C. PEA/wou HZvH/v 5. CnePfwTE/P ATTORNEY.

July 13, 1937. G. c. PEARSON ET A.

ROCK DRILL FEEDING MECHANISM 4 sheets-sheet 3 Filed March 12, 1934 m A x e luxlllli,

ZV/wv 3. CARPE/v TH? BY I A ri; (TgTmM July 13, 1937. G. c. PEARSON 'ET An. 2,086,634

4 ROCK DRILL FEE-'DING MECHANISM Filed March l2, 1934 4 ySheets-Sheet 4 i" y d l Gas/*Av C. Pff-Anson /wm/ 5. CHRPENT@ gaging their respectiveracks, locking the 60,

Patented July 13, 1937 PATENT OFFICE n 2,086,634' Y ROCK DRILL FEEDING MECHANISM Gustav C'. Pearson and Ivan S. Carpenter, Denver, Colo., assignors to Gardner-DenverrCompany, Denver, Colo., a corporation of Delaware Application March 12, 1934, Serial No. 715,149

28 Claims.

The invention relates to improvements in rock drills and is more particularly directed to means for automatically feeding such drills to and from their worlfr.` l

'The object of the present invention is to provide a novel and effective means, independent of any `action of the drilling unit, for feeding a drilling unit to and from its work.

Another object of the invention is toprovide fluid actuated means under the full control of the operator for moving a drilling unit longitudinally of itssupport.

Still another object of the invention is to provide fluid operated means for moving a rock drill upon its support, sai-d means being adapted to move the drill in any longitudinal direction, to lock the drill against movement, and to free the drill so that it might be moved by hand upon its support. f

Another object of the invention is to provide automatic feeding means for a drill operable at such periods as to assure the correct striking relation between the drill hammer and the steel.

Further objectsof the invention will be apparent from the description` made hereinafter, and to all of these-ends the invention consists cf the features Aof construction, arrangement of parts, and combination of elements substantially as describedfin the'specication, claimed and shown in the accompanying drawings in which:

Figurev v1 is a side elevation of a rock drill mounted-upon a support and having connected thereto one-'example of the feeding device constituting the present invention.

Figure 2 is a top plan view of the support showingv positioned therein reversely arranged racks andthe means for permitting longitudinal movement of the racks with respect to the support.

."Figure 3 isan enlarged vertical sectional view showinga portion of a drill with the feeding device' connected thereto. y

Figure 4 is a diagrammatic view illustrating one form of an automatic valve for controlling the movement of the 'piston in the feeding device. Figure .5 is la sectional view on the line 5-5 of Figure 3,-through the cylinder, piston and valve of the. feeding device. y,

1 Figure 6 .is a vertical sectional view through a portio-nof the feeding device showing the hand controlled lever for moving the various pawls into and .out of engagement with their respective racks..

Figure 7 is a plan view on the line 'l-'l of Figure 6 showing. the staggeredarrangement of the various rack engaging pawls.

l, Figure 8 is a perspective view illustrating in detail the stationary pawls carried by the cylinder ofthe feeding device and shows both'pawls enn device against movement.

Figure 9 is a similar view showing in detailk the pawls carried by the piston with one pawl engaging its rack, while the other pawl is' elevated.`

Figure l0 is a sectional view on the line Ill- I0 of Figure 3 showing the stationary pawls lowered as in Figure 8.

Figure 11 is a sectional view on the line Il-H of Figure 3 showing the pawls carried by the piston in a lowered position.`

Figure 12 is a sectional view on the line |2-,I2 of Figure 2 and illustrates the manner of mounting the -rack plate within the support, and

- Figure 13 is a perspective view showing a portion of the rack plate.

Briefly, the present invention contemplates the provision of a iiuid operated feeding device adapted to .be associated with ka rock drill to move the same to and from its Work. It will, of course, be understood that in the operation of the'rock drill as the steel advances into the rock it is they purpose of the feeding device to automatically feed the drill forward, maintaining it in such a position with respect tothe work as to obtain the proper striking relation of the drill hammer with the steel. In the yaccompanying drawings the device is shown as a part of the drill, this is merely one modification. However, such a structure tends to simplify the unit as it combines the two main control valves in one. If desired, the feeding device may be wholly independentof the. -drill and connected thereto in anyy suitable manner, jor it may merely slide in the support and abut the drill feeding it forward.

In the present embodiment, the feeding device includes acylinder `having therein a reciprocatory piston, controlled in its movements by an automatic lvalve of any desired structure. The device is slidable in the guideways of a support, in rear of the drill, and is provided with two sets of selectively controlled pawls, one set being mounted in an end wall of the feed cylinder, while the other set is mounted in a` head carried by the piston, `both sets being engageable -with racks inthe bottom of the support. It is through the medium of these pawls and racks that movement of the drill, and device, longitudinally of the support is accomplished.

The pawls are controlled at the will of the operator and may be moved with lrespect tol their racks so as to lock the device against either forwardy or rearward movement, or against movemounted for movement in the shell 5.

` present embodiment the drill includes a cylinder 5 indicates a conventional mounting shell having a cone 6 by which the shell may be suitably secured to a mounting. The shell 5 includes a bottom 'I an-d upstanding side walls 8, the inner faces of the latter being provided with longitudinally extending grooves constituting guideways 9 in which the rock drill and its feeding device, hereinafter described, are positioned for longitudinal movement.

The upstanding walls of the shell 5 are further provided, on their inner faces adjacent the bottom 'I, with longitudinal grooves IIJ receiving therein projections I I formed upon the side edges of a removable plate I2. The upper face of this plate I2 carries reversely arranged racks |43 and I4.

4To maintain the rack plate I2 in place within the shell and yet providel a slight longitudinal movement of the plate, the ends of the guide shell are closed by cross arms I5 maintained to the shell by bolts I6 passing through outstanding ears II. The bolts I6 extend beyond the ears I'I and have positioned thereabout, between the ears II and Y theusual lock nuts I8, coil springs' I9. With this structure it will be apparent that the rack I2,

even though its ends abut the cross arms l5, has a slight longitudinal movement, due to the yielding action of the cross arms, with respect to the guide shell, and this movement reduces the shock and strain upon the racks during the engagement of the various operating pawls therewith.

In Figures 1 and 3 a rook drill-20 is shown of any desired constructionv and which may e In e 2| having the usual outstanding flanges, not shown, which slidably engage the guideways 9 of the yshell 5. The cylinder has therein a reciprocatory piston hammer 22 intended to impart blows to a drill steel 23 supported in the front end of the drill. The movement of the hammer being controlled by a suitable automatic valve', the chest of which is shown at '24. In rear of the chest 24 the cylinder 2l has positioned therein suitable means, indicated at 25, for imparting rotary movement to the hammer and ultimately the steel. To move the drill 20 longitudinally of the shell 5 there is arranged, in rear of the g cylinder 2 I, a complete fluid operated motor generally indicated at 26.

Referring more particularly to Figure 3 the feeding motor includes a oylindricalchamber 2'I having therein a reciprocatory piston 2B controlled in its movement by an automatic valve 29 of any desired type. The chamber 21 is formed inan intermediate plate 39 and end sections 3I and 32. The end section 32 is provided with outstanding anges 33, Figure 10, for engagement inthe guideways 9 of .theshell 5, to maintain the feeding device in alignment with the rock drill.

.It willbe observed that the piston 28 is provided with front and rea-r extensions 34; andv 35, the former reciprocating within a bore provided 2 in the. end plate3l for the purpose of 'preventing any misalignment of the piston within the cylinder when lateral strain is applied to the extension 35 in a manner hereinafter set forth.

In rear of the end plate 32 there is positioned aback Vheadi36 .spaced from the plate 32by an integral: hood structure 3l, serving to enclose the free end of the piston'extension 35. The back head 36 hasfmounted therein the usual fluid control valve 38, the water tube 39 which conveys s water from a suitable rear connection to the steel and a manually operated lever for moving the rack engaging pawls.

The various sections forming the feeding device are connected to the rock drill and 'made a part thereof by suitable side rods 40.

Referring now to Figures 3, 6, 8, and 9 it will be observed that two sets of rack engaging pawls are provided, one set, referred to hereinafter as the stationary pawl, being mounted for vertical movement within the end plate 32, more clearly shown in Figure 10. All pawls being provided with enlarged feet having teeth engageable with their respective racks and held in such engagement by suitable springs.

As shown in the above gures, the pawls constituting the stationary set are indicated at 4I and 42, 'Ihese pawls are spaced apart and their adjacent sides are provided with undercut por-` tions forming lips 43, adapted to be engaged'by outstanding flanges 44 formed longitudinally upon a control shaft 45,*positioned between the pawls'and mounted for oscillatory movement in the back head 36 and a socket 46 formed in the end plate 32. The shaft 45 is provided Awithan operating handle 4'I.

To hold the shaft k45 in any desired position, to elevate or lower the pawls, there is positioned about the shaft a removable taperedbearingl held against rotary movement, with respect to the back head, by a projection 49 fitting withiny a slot 50 formed in the back head. lThe front edge of the bearing 48 carries V shaped notches 5|,f52 and 53, any one of rwhich beingadapted to receive therein an outstanding pin 54 fixed in the shaft 45. "Io maintain engagement of the pin 54 within any desired notch, the free end of the shaft 45 is providedfwith a bore having positioned therein a spring pressed plunger 55, the end of which abuts the end wall of the V.shaft socket 46 formed in -the end plate 32. f

The rear extension `35 of the piston has-'detachably connected thereto Aa dependingfhead plate 56 having a bore 5l through which the shaft 45 passes. Upon lateral sides of the bore 51 there are provided vertical sockets having therein spring pressed pawls 58 and 59. These pawlsibeing of a structure similar to those previously described and provided with lips` 69 adaptedto -be engaged by the outstanding flanges :44 of the shaft 45. The headplate 56 and the piston'extension 35 being vcovered at all times, and during their movement, by the hooded portion 31 ofthe back head 36.

. Referring to the means for ,controlling Athe movement of the various pawls it will be observed that Figures 1 and 3 disclose the pawls forv feeding the drill and device forward as engaging the rack I4. .-To secure this functioning position of the pawls, the operating handle 4`I is swung. to the left-to permit the pin 54, carriedgby the shaft, to engage the notch 53. shaft lowers the stationary pawl 42 and. the pawl 59 carried by the piston, while'the stationary pawl 4I and the piston carried pawl 58 are: raised out of engagementwiththe rack I3. Suohposltion of the pawls," upon operation of the piston, moves the drill and feeding device forward-'of the guide shell step` by step.

- After the drill hasmoved forwardly the desired distance, the operating handle 41 is then moved to the `extreme right position whereupon the shaft pin 54 will engage the V notch 5I. Suchv movementof thev shaft' 45 llowers the stationary pawl'4I andthe piston carried pawl 58 to engage the rack I3, at the same timeraising-pawlst- Such oscillation of the Movement of the piston with the pawls in these positions tends to move the drill and feeding` device rearwardly of the support. f

It is, of course, understood that in the forward and rearward movements of the feeding device the hammer of the drill continues in operation, and that it will play a very important part in withdrawing the steel from the hole, giving to. the steel suiiicient jar or vibration to free it should it become stuck.

At some periods of operation it is vdesirable to lock the feeding device against movementand to accomplish this the operating handle is moved to permit the engagement of the shaft pin 54`with the V notch 52, thus oscillating the shaft 45 to the position shown in Figure 8, whereupon the pawls of both sets will be free to move downward under the influence of the springs to engage their respective racks.

At certain periods vin the operation of a drifting drill it is customary for the operator to grasp the drill and move the same longitudinally'upon its support; this is merely a time saver, as it eliminates the turning of the usual hand crank. Such movement of a drill equipped with this feeding device is permissible. To accomplishthis, assuming that the operator has drilled the hole and wishes to withdraw 'the drill from the steel without utilizing the feeding device, the operating yhandle of the shaft 45 is oscillated to permit the pin 54 to engage the V notch 5|, whereupon the pawls 42 and 59 which engage the rack I4 are elevated and the pawls 4I and 58 vare lowered to engage the rack I3. With the pawls in this position and the throttle valve 31 closed, the operator may ythen grasp the rear end of the unit and pull the drill backward upon itssupport. To manually move the unit forwardly, the pawls 42 and 59 are lowered, while the pawls 4| and 58 are elevated.

It is, of course, apparent that in the reciprocation of the piston and the engagement of the pawls with the racks that some shock is imparted to the rack plate. To eliminate or reduce this shock and breakage of the pawl and rack teeth, the rack plate is resiliently mounted as previously described.

The automatic distributing valve indicated at 29 is positioned within a bore 6| formed in the intermediate section 30 and closed by the end plates 3| and 32. With the various parts in position as shown in Figure 3 operating fluidl passes from the control valve 38 through a passageway 62 to an annular groove 63 arranged in the front face o'f the end plate 3|. From this annular groove 63 fluid passes to the automatic valve of the rock drill and through the passageway 64 to the bore 6| in which the valve `29 of the feeding device operates. Entrance to the bore for the motive iiuid being supplied through port 65 as shown in the diagrammatic view constituting Figure 4. v i

It will be observed that Figure 3 illustrates the piston 28 and valve 29 in one of their two functioning positions while Figure 4 shows them in the other position.

With the piston andvalve in position as shown 'in Figure 4 the general operation of the valve is inthe following manner, motive fluid passes freelyfrom the port 65 through the valve into the passageway 66 leading to the piston chamber 21 in? rear of the piston. The piston will then be driven forwardly, the exhaust to atmosphere from the yfront piston chamber -l1 being through the passageway 61, bore 6|, valve 29 and exhaust port 68. When the piston is in its front position with the automatic valve shifted forwardly motive fluid then passes from the supply port 65 through the passageway 61 and into the piston lchamber 21 in front of the piston while that portion of the piston chamber 21 in rear of the piston is open to atmosphere through the passageway 66, bore 6I and'eXhaust port 69. The piston thenr moves rearwardly. This cycle of operation then repeats itself.

For the purpose of effecting the shifting movements of the valve there'is provided passageways 1U and 1| which connect with intermediate portions of the piston chamber 21 and are covered and uncovered by the piston during its movement. With the valve in position as shown in Figure 4 and motive fluid being supplied through the passageway 66 to the rear face of the piston, the piston moves forward and the passageway 10 is uncovered, permitting fluid to flow to the front face of the valve moving the valve to its second functioning position, that shownin Figure 3, whereupon uid will then pass from the supply port 65 through the passageway 61 to the frontface of the piston. As the piston moves rearward the passageway 1| is uncovered, permitting active fluid to engage the rear face of the valve moving the same to the position shown ink Figure 4, whereupon the cycle is repeated.

Assuming now that the various parts of the feedingA device are in position as shown in Figure 3, whereupon the drill is to move forwardly of the guide'shell, motive fluid from the passageway 64 is admitted by the valve 29 to the front piston chamber 21, through the passageway 61, and inasmuch as the pawl 59 carried by the piston is in engagement with the rack I4, movement of the piston rearwardly is prevented. However,

. the fluid in the chamber 21 will be active upon the end of the cylinder'bore moving the drill forward equal to the degree of penetration of the steel, operated upon by the hammer 22 of the drill, into the ore. When the unithas moved sufficiently the passageway 1I is uncovered, permitting motive fluid to pass to the rear end of the automatic valve, moving the same tothe position shown in Figure 4. After the valve has shifted to this second position, motive fluid is then admitted into the rear piston chamber 21, whereupon the piston moves forwardly andthe pawl` 59 carried thereby engaging an advanced portion of the rack I4. During the forward `movement of the piston the passageway 10 is feeding device the pawl 42 engaging .the rack I4 prevents any rearward movement of the drill and device which may be affected by vibration or during the movement of the piston to-'secure a new engagement with the rack.

l Upon the reverse movement of the drill the shaft 45`is oscillated so that the pawls 4| and 5B will engage the rack I3, while the pawls 52 and 59 will be elevated. In this position of the pawls, motive fluid will be active in a manner similar to that described in the forward movement of the unit, with'the exception that inasmuch as the pawl 58'carried by thel piston prevents the piston from moving forwardly, fluid will be active upon the rear endwall of the pistonphamber, moving the unit until the passagewayd is uncovered, tripping the-valve and admitting luidto;

the front faceV of the piston, moving the. samev rearwardly and permitting the paWl 58 to engage an advanced rear portion of the rack 13. Upon i the rearward-movement of the piston the passage- Way 'll is uncovered. admitting uid from the chamber 2l to the rear end face of. the valve, tripping the valve tothe position-shown inFigure fi, whereupon the cycle of operation just described is repeated. The pawl ,4l in this operation prevents Aundue. forward movement of the unit.

From the foregoing it is thought'that theconstruction, operation and `many advantages of the. herein described invention will be apparent to those skilled in the art Without further descrip,-v

.tion, and it will be understood that various changes in the size, shape, proportion and minor details of construction may be resortedto Without departing from the spirit or sacrificing any of the advantages of the invention. v*What We claim is: Y 1. The combination With a rock drill support having a guideway, of a rock drill slidable therein, a feed motor for the drill including a constantly reciprocatory piston, said feed motor bei pawls carried by thecylinder yand piston and engageable with the support, and sai-d cylinder Vand piston pawls when moved With respectto-zeach other by uid alternately engaging portions of thesupport for moving the drill thereupon. v

3. The combination with a rock drill support, of

` a drill slidable thereon, a feed motor for the drill comprising a cylinder member xed to the drill and a reciprocatory piston member'movable inthe cylinder, and mechanism carried by the cylinder .and piston for alternatelyengaging portions of the support to move the drill thereupon. 4. The combination with a rock` drill-support. of a drill slidable thereon, a feed motor for the drill comprisinga cylinder member -xed to the drill and a reciprocatory piston member movable in the cylinder, and selectively controlled mecha- Y nisms carried by the cylinder and `piston for alternately engaging portions of the support to move the drill in opposite directions-thereupon.

5. The combination With a rockdrill support, of a drill slidable thereon, a feed motor .forthe jdrill comprising a cylinder member fixed to the `drill and a reciprocatory piston therein, a racklonfthe support, and pawls carried by the cylinder and piston for alternatelyengaging the rackv tomove the drill upon'the support.

6. A drilling unit vcomprising afpairvof'rzlongitudinally arranged cylinders; a` constantlyfreciprocating piston in each cylinder, Aone -foil striking the drilling steel and the other lfor imparting motion to-the unit; a common valve controlling the flow of fluid to each cylinder; a supportifor-.the unit; and means carriedby the last named piston and its cylindery for alternately engaging the suprport to move the'unit longitudinally.thereupon.

'7."The combinationzwith a rock, drill support, of a drill 'slidable thereon, a-feed.;motorforthe drill comprisingza cylinder member fixed to' the. drill and ya .constantly reciprocating piston memv ber movable inthe cylinder, reversely a-rrangedv racks on the support,` selectively, controlled pawls carriedlbyrthe piston, and cylinder and engageable.with .the racks to Vmove the drill in reverse direction thereupon,v andsaidpawls being further;.controlled to' permit manual movement of thedrill upon the support. y

8.-.The .combination With arock drill support, of a drill slidable thereon, a feed motor; for the drill .comprising afcylinder member fixed to the drill and arreciprocatory piston member movable in the cylinder, reversely arrangedrracks onv the support, seleotivelycontrolled pawls carried bythe piston and cylinder and engageable with the racks to move the drill inl reverse direction thereupon, and saidpavvls being-further controlled to lock the -drillagainst movement `with lrespect-to the support. v .i y

9. The combination With a rock drill support, of axdrill slidablethereupoma feed motor forthe` drillscomprising a; cylinder .member iixed'to the drillY an-dphaving a constantly reciprocating piston therein, reversely arranged racks on'thesupport,.movable pawls .carried by vthe pistonrand cylinde'riqand engageablezwith the racks tomove the drill in Areverse directions thereupon,.anv os. cillatory element adjacent the pawls, and-said elementcontrolling the engagement of the pawls with the racks. L i' i l0. lThe combination with a rock drillsupport, of a drill slidable thereupon, a feed motorfor the drill comprising a cylinder member ixed to the drill and having a constantly reciprocating piston therein, reversely arranged Vracks on the support, vertically movable pawls carried by `the piston and .cylinder and engageable With the racks to move the drill in reverse directi'onsthereupon, saidv pawls arranged in pairs and having an oscillatory member therebetvveemand said oscillatory memberv when moved ,permitting the engagement of onepgavvl from.` each pair with its respective rack and the disengagement of the remaining pawls from=their respectiverack.

1l. A drilling unit comprising a pair of fluid operated motors eachwhaving a pistornone for striking a steel and the other for yimparting `motion to 'the unit, a support-for the unit, and means carried bythe motion imparting, piston and lmotor to lalternately engage the. support `for moving the unit thereupon.

v12. A drilling 'unit` comprising., a .pair of fluid operated-.motors each :havinga piston, `oneior :striking a steel andthe other for imparting .motion to the unit, a'support for the unit,` elements carried by the. motionimparting piston and Vmotor for alternatelyengaging the-support to move the unit tlfiereupon,v andjmeans operating'said elements to vcontrol vthe directional movement of thefunlt.. l

13. The :combination with .a roel: drill support, of a rock drill slidable thereupon, a: feed motor for the drillincluding a continuously re- .ciprocatingpistom said feed motor being slidable upon the. support and. adjacent the drill, and said piston engaging the support to move thedrill stepbystep llongitudinally thereupon.

14L-The :combination with. a. rock vdrill..support of. a.-ro'cl: drillslidable thereupon,Y a feed .motor forthedrillA including aj piston movable at-certainintervals .With respect to the-support,

4aivalve controlling thefflow ofluidactive upon .theipiston,said ,piston having elementsy engaging fhO-SUPDQTi-.means .TGSQQDSYQ t0 thmQVe' Cil ment of the piston for actuating said valve, and the intervals during which the piston moves being governed by the movement of the drill upon lthe movement of the drill upon thesupport.

16. The combination with a. rock drill support of a rock drill slidable thereon, a feed motor for the drill having a reciprocatory piston member therein, and selectively controlled mechanisms carried by the motor and piston for alternately engaging portions of the support to move the drill thereupon.

17. Rock drill advancing means comprising in combination a fluid operated device having piston and cylinder elements, one of which elements is securable to the drill, means to admit driving fluid alternately to opposite sides of the piston substantially at the ends of the piston and cylinder strokes, and means separately to hold the said two elements against movement in one direction to enable them to perform alternate step by step advancing movements in the opposite direction when the said device is operative. l

18. Rock drill advancing means comprising in ycombination a uid operated device having piston and .cylinder elements, one of which elements is securable toI the drill, means to admit driving fluid alternately to opposite sides of the piston substantially at the ends of the piston and cylinder strokes, and a pawl and ratchet mechanism operatively connected to each of the said two elements separately to prevent retrograde movement of each of them Whilst the other makes a relative advancing movement under the action of the operating fluid.

19. Rock drill advancing means comprising in combination a fluid operated device having pistn and cylinder elements one of which is mounted to move with a drill and has a part formed as a valve casing, a valve in said valve casing for controlling the operation of the device, means to convey driving fluid to' the valve casing, and means separately to hold the said piston and cylinder elements against movement in one direction to enable them to perform alternate step by step advancing movements in the opposite direction when the said device Ais operative.

20. Rock drill advancing means comprising in combination a fluid operated device having piston and cylinder elements one of Which is mounted to move with a drill and has a part forme-d as a valve casing, a valve in said valve casing for controlling the operation of the device, means to convey driving fluid to the valve casing, and a pawl and ratchet mechanism operatively connected to each of the said piston and cylinder elements separately to prevent retrograde movement of each of them whilst the other makes a relative advancing movement under the action of the operating iluid.

21. Rock drill advancing means according to claim 17 comprising also means to enable the piston and cylinder elements to perform alternate step by step retracting movements at will.

22. Rock drill advancing means according to claiml comprising also a further pawl and ratchet mechanism toprevent forward movement of the fluid operated `device and means respectively to render the further (i. e. reverse acting) and also the forwardly acting (i. e. to prevent retrograde movement) pawl and ratchet mechanisms inoperative as desired.

23. Rock drill advancing means according to claim 20 comprising also a reverse acting pawl and.- ratchet mechanism for preventing forward movement operatively connected to that element of the fluid operated device free to move relativelyto the drilL'and means separately to render inoperative as desired both the forwardly acting and the reverse acting pawl and ratchet mechamsm.

24. Rock drill advancing' means comprising in combination a uid operated device having piston and cylinder elements, `one of which elements is securable to the drill, means automatically operative substantially at the ends of the piston and cylinder strokes to admit driving fluid alternately to opposite sides of the piston, and means separately to hold the said two elements against movement in one direction to enable them to perform alternate step-by-step advancing movements in the opposite direction When the said device is operative.

25. Rock drill advancing means comprising in combination a fluid operated -device having piston and cylinder elements, one of Which elements is securable to the drill, means automatically operative substantially at the ends of the piston and cylinder strokes to admit driving fluid alternately to opposite sides of the piston, and a pawl and ratchet mechanism operatively connected to each of the said two elements separately to prevent retrograde movement of each of them while the other makes a relative advancing movement under the action of the operating fluid.

26. A drilling unit comprising a pair of fluid operated motors each having a piston, one for striking the steel and the other for imparting motion to the unit, a support for the unit, means actuated by the motion imparting piston to move the unit upon the support, and a mechanism coperating with saidmeans for controlling the directional movement of the unit upon the support.

27. A drilling unit comp-rising a pair of fluid operated motors each having a piston, one for striking the steel and the other for imparting motionto the unit, a support for the unit, means actuated by the motion imparting piston to move the unit upon the support, and a manually actuated mechanism controlling said meansl for rendering Vthe latter inactive upon continued movement of the motion imparting piston.

.28. A rock drilling unit comprising a pair of uid operated motors each having a piston, one for striking the work performing steel and the other for imparting motion to the unit, a support for the unit, means controlling the movement of the last said piston, means: responsive to the movement of the drill for actuating said piston, and the last said means being controlled at certain periods of Work performed by the steel.

GUSTAV C. PEARSON. IVAN S. CARPENTER. 

